1. Field of the Invention
This invention relates to methods and apparatus for cable testing in communication systems. More particularly, the invention relates to methods and apparatus for detecting a failed cable end and operator of the cable connected between remote switching centers in communications systems.
2. Description of the Prior Art
Today's communications systems include transmission paths, for example, T3 lines linked together by network switching centers serving multiple-access providers. In many instances, a network switching failure can be attributed to a bad or disconnected T3 cable interconnecting remote switching centers. One problem with such a failure is detecting and identifying the cable end at which the failure has occurred. Another problem is determining the access provider responsible for the failed cable and restoring service to the switching center.
Prior art related to detecting and identifying faults in cables connected to remote switching centers includes the following:
U.S. Pat. No. 4,413,229 issued Nov. 1, 1983, discloses a method for locating faults or failures in RF coaxial cable TV transmission facilities. A fault locator signal frequency is inserted into the cable system and low magnitude signals are emitted by means of a bandpass filter and radiating element. The radiated RF is detected to determine coaxial cable system operation. Bandpass filters and radiating elements are located at each point to be tested. Intentional, controlled, discriminate RF radiation is used for fault detection in conjunction with a coupler bandpass filter.
U.S. Pat. No. 4,524,321 issued Jun. 18, 1985, discloses a method of detecting open-wire or improper wire connections in a group of wires interconnecting first terminals of a first bank with second terminals of a second bank. Integrity and connection of the cable wires are checked for shorts of the wires to ground, to battery wiring between each other, and for opens and mis-connections or cross-connections of the wires. Recognition circuits control, analyze, and display test results to apprise an operator(s) stationed at either or both ends of the cable.
U.S. Pat. No. 5,282,237 discloses a ring communications network having a plurality of line concentrators each including a ring-in port, a ring-out port, and a plurality of station ports. The network is adapted to detect a fault in a trunk cable between concentrators and re-configure the ring to bypass that fault. Fault detection is accomplished by injecting a phantom DC voltage at the ring-out port and sensing whether current due to that voltage is present at both the ring-out port and the ring-in port of the next adjacent concentrator in the ring.
None of the prior art discloses methods and apparatus for detecting and locating which end of a cable connected between remote terminals has failed and the identity of the service provider of the failed cable.